Physiological processes of plants infected by vascular pathogens are mainly affected by vascular bundle obstruction, decreasing the absorption of water and nutrients and gas exchange by stomatal closure, and inducing oxidative cascades and PSII alterations. Chitosan, a derivative of chitin present in the cell wall of some organisms including fungi, induces plant defense responses, activating systemic resistance. In this study, the effect of chitosan on the physiological and molecular responses of tomato plants infected with Fusarium oxysporum f. sp. lycopersici (Fol) was studied, evaluating the maximum potential quantum efficiency of PSII photochemistry (Fv/Fm), photochemical efficiency of PSII (Y(II)), photochemical quenching (qP), stomatal conductance (gs), relative water content (RWC), proline content, photosynthetic pigments, dry mass, and differential gene expression (PAL, LOXA, ERF1, and PR1) of defense markers. A reduction of 70% in the incidence and 91% in the severity of the disease was achieved in plants treated with chitosan, mitigating the damage caused by Fol on Fv/Fm, Y(II), and chlorophyll contents by 23%, 36%, and 47%, respectively. Less impact was observed on qP, gs, RWC, and dry mass (16%, 11%, and 26%, respectively). Chitosan-treated and Fol-infected plants over-expressed PR1a gene suggesting a priming-associated response. These results demonstrate the high potential of chitosan to protect tomato plants against Fol by regulating physiological and molecular responses in tomato plants.

Biological control (BCAs) such as Trichoderma spp. minimize fungicides inputs in agriculture, and increase both the plant nutrition and the efficacy against fungal diseases. Novel bioproducts in crop management are called to guarantee sustainable antagonism activity of BCAs and increase the acceptance of the farmers. The encapsulation in polymeric matrices play a prominent role for providing an effective carrier/protector and long-lasting bioproduct. This research aimed to compare two hydrogel capsules prototypes based on alginate (P1) and amidated pectin (P2), containing Trichoderma koningiopsis Th003 conidia. Capsules were prepared by the ionic gelation method and calcium gluconate as crosslinker was used. The capsules were characterized by various properties such as conidia releasing at different pH values, drying conidia survival, storage stability, and biocontrol activity against sheath blight (R. solani) in rice. P2 prototype provided higher survival to Th003 up to 98% in fluid bed drying, faster conidia release at pH 5.8, storage stability > 6 months at 18°C, and a disease reduction up to 67%. Amidated pectin provides advantages on drying survival and conidia release at pH 5.8. Both biopolymers facilitate the antagonistic activity against R. solani, and therefore can be incorporated in hydrogel capsules for novel bioinoculants development. This research highlights the knowledge regarding the influence of biopolymer in hydrogel capsules on survival and shelf-life of Trichoderma spp conidia.

Physiological processes of plants infected by vascular pathogens are mainly affected by vascular bundle obstruction, decreasing the absorption of water and nutrients and gas exchange by stomatal closure, and inducing oxidative cascades and PSII alterations. Chitosan, a derivative of chitin present in the cell wall of some organisms including fungi, induces plant defense responses, activating systemic resistance. In this study, three chitosan molecules (low, medium and high molecular weight) at different concentrations (0.5, 1, 1.5, 2, 2.5 and 3 mg mL-1) were assessed by in vitro tests against Fusarium oxysporum f. sp. lycopersici (Fol). Concentrations higher than 1 mg mL-1 were found to inhibit significantly the mycelial growth of Fol, with 95.8% of inhibition using chitosan with high molecular weight (3 mg mL-1). For in planta assays, chitosan treatment (low molecular weight 2.5 mg mL-1) showed significantly lower incidence and severity of wilting disease symptoms, 70 and 91%, respectively, compared to healthy plants used as a negative control. The effect of chitosan on the physiological and molecular responses of tomato plants infected with Fol was studied, evaluating the maximum potential quantum efficiency of PSII photochemistry (Fv/Fm), photochemical efficiency of PSII (Y(II)), stomatal conductance (gs), relative water content (RWC), proline content, photosynthetic pigments, dry mass, and differential gene expression (PAL, LOXA, ERF1, and PR1) of defense markers. A reduction of 70% in the incidence and 91% in the severity of the disease was achieved in plants treated with chitosan, mitigating the damage caused by Fol on Fv/Fm, Y(II), and chlorophyll contents by 23, 36, and 47%, respectively. Less impact was observed on gs, RWC, and dry mass (55, 11, and 26%, respectively). Chitosan-treated and Fol-infected plants over-expressed PR1a gene suggesting a priming-associated response. These results demonstrate the high potential of chitosan to protect tomato plants against Fol by regulating physiological and molecular responses in tomato plants.

La pudrición blanca producida por <em>Sclerotium cepivorum</em> es la principal limitante del cultivo de ajo en Colombia, causando pérdidas superiores al 50%. La ausencia de semilla de calidad contribuye a su diseminación e infestación en áreas de siembra, siendo la principal estrategia de control la aplicación de fungicidas, por ende, es necesario integrar alternativas de manejo orientadas a su sostenibilidad. Así, el objetivo de este estudio fue determinar bajo condiciones controladas el potencial de control de <em>S. cepivorum</em> con antagonistas microbianos y aceites esenciales. Se determinó en PDA suplementado con cada aceite el efecto sobre el crecimiento del patógeno y para los antagonistas su capacidad para degradar esclerocios. Igualmente, en suelo infestado con esclerocios se determinó el efecto de las aplicaciones de los antagonistas y aceites seleccionados sobre la reducción de incidencia y mortalidad. Los resultados mostraron que la exposición al aceite de eucalipto (10000 ppm) y orégano (200; 250 ppm) inhibió en un 92% el crecimiento del patógeno; en tanto, que los antagonistas colonizaron más del 95% de los esclerocios, provocando su degradación. Mientras que en suelo infestado presentaron un control entre 30 al 70%, siendo <em>Trichoderma asperellum</em> Th034 el que presentó la menor incidencia y mortalidad (21%).

Introducción. En Colombia, la producción de ajo se ve afectada por patógenos, principalmente Sclerotium cepivorum, el cual se disemina por el material de siembra. Es necesario establecer tecnologías de bajo costo que permitan controlar este patógeno. Objetivo. Evaluar dos métodos de termoterapia, termoterapia por calor seco y termoterapia por inmersión en agua, para disminuir la presencia de S. cepivorum en semilla de ajo y su efecto sobre características agronómicas de plantas emergidas a partir de bulbillos tratados. Materiales y métodos. Este trabajo se llevó a cabo en el Centro de Investigación Tibaitatá de la Corporación Colombiana de Investigación Agropecuaria (AGROSAVIA), ubicado en Cundinamarca, Colombia, durante el primer semestre del 2019. Se evaluaron nueve tratamientos; cinco en termoterapia por calor seco: 35 ºC por 12 h, 35 ºC por 129,6 h, 50 ºC por 48 min, 5 ºC por 20 días, 38 °C por 1 h; dos en termoterapia por inmersión en agua caliente: 48 °C por 30 min, 50 °C por 20 min y dos controles: desinfección química (tebuconazol) y temperatura ambiente (20 ºC por 20 días), en un diseño en bloques completos al azar. Se evaluó brotación de bulbillos y crecimiento de las plantas de ajo después de aplicar termoterapia a la semilla y viabilidad de esclerocios de S. cepivorum. Resultados. El almacenamiento de la semilla a 5 ºC por 20 días aceleró su brotación, alcanzó una germinación de 80 % a los cinco días, mayor número de hojas y acumulación de biomasa. La germinación de esclerocios estuvo entre 33 y 67 %; el tratamiento que presentó la menor incidencia fue 35 ºC por 129,6 h (33 %). Conclusión. El tratamiento de termoterapia por calor seco a 35 °C por 129,6 h mostró potencial en la reducción del inóculo de S. cepivorum en semillas de ajo.